<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        header,
        nav,
        footer,
        aside,
        article {
            background-color: #97b253;
            border-radius: 20px;
            border: 2px solid #839252;
        }
        header,
        nav,
        footer {
            width: 1200px;
            height: 100px;
            margin: 15px auto;
        }
        .content {
            width: 1200px;
            height: 400px;
            margin: 15px auto;
        }
        aside {
            float: left;
            width: 400px;
            height: 100%;
            margin-right: 15px;
        }
        article {
            float: left;
            width: 777px;
            height: 100%;
        }
        section {
            width: 400px;
            height: 75px;
            background-color: #c9d6b1;
            border: 2px solid #8f9c74;
            border-radius: 20px;
            margin: 200px auto 100px;
        }
    </style>
</head>

<body>
    <header></header>
    <nav></nav>
    <div class="content">
        <!-- 侧边栏 -->
        <aside></aside>
        <!-- 内容 -->
        <article>
            <!-- 定义文档某个区域 -->
            <section></section>
        </article>
    </div>
    <footer></footer>
</body>

</html>